/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.flink.runtime.io.network.partition.hybrid.tiered.tier;

import org.apache.flink.runtime.io.network.buffer.Buffer;
import org.apache.flink.runtime.io.network.partition.hybrid.tiered.common.TieredStoragePartitionId;
import org.apache.flink.runtime.io.network.partition.hybrid.tiered.common.TieredStorageSubpartitionId;
import org.apache.flink.runtime.io.network.partition.hybrid.tiered.storage.AvailabilityNotifier;

import java.io.IOException;
import java.util.Optional;

/**
 * The {@link TierConsumerAgent} is the consumer agent of each tier in tiered store, which could
 * read data from responding tier.
 */
public interface TierConsumerAgent {

    /** Start the consumer agent. */
    void start();

    /**
     * Get buffer from the consumer agent.
     *
     * @param partitionId the id of partition.
     * @param subpartitionId the id of subpartition.
     * @param segmentId the id of segment.
     * @return buffer.
     */
    Optional<Buffer> getNextBuffer(
            TieredStoragePartitionId partitionId,
            TieredStorageSubpartitionId subpartitionId,
            int segmentId);

    /**
     * Register the notifier to notify the availability of a subpartition.
     *
     * @param notifier to notify availability.
     */
    void registerAvailabilityNotifier(AvailabilityNotifier notifier);

    /** Close the consumer agent. */
    void close() throws IOException;
}
